The phylum of Chordata encompasses a vast and diverse group of organisms. In order for an organism to be classified as a chordate, it must possess all five characteristics of a chordate at some stage in its lifetime; though many chordate traits are lost with further development. The first of these unifying characteristics is the presence of the notochord. This is a rod which runs the length of the organisms body to provide a ridged yet flexible support structure. Chordates will also possess a dorsal hallow nerve chord. As the name suggests, this is a hallow chord which runs the length of the body and sits dorsal to the notochord. The third trait all chordates have is some sort of iodine fixing gland. In many species this may be an endostyle. For humans this is our thyroid gland. Another trait is the presence possess pharyngeal gill slits, which are located along the pharynx. Lastly, all chordates will possess a post-anal tail at some point in their lifetime.
Comments
This gives a good, quick
This gives a good, quick summary of what a Chordota is. The sentences are a little choppy and I think you could use a variety of transitions to make the paragraph flow more smoothly. I would also try to be more descriptive when describing the traits/charactersitics because not everyone is a biology major or has familiarity with many of the terms used.
Run-On Sentence
The paragraph does an efficient job summarizing the topic. The only suggestion I have is that the second sentence in the paragraph is a run-on sentence. I suggest splitting into two senetnces to make the paragraph flow better.
Flow
Since this paragraph is describing five characteristics common to chordates, I would suggest naming the five characteristics in the first sentence, and then using the rest of the paragraph for describing each one in more detail.